The present invention relates to a material/quantity requirements arithmetic determination system for determining arithmetically a material/quantity requirements schedule in order to determine various types of parts and raw materials required for manufacturing an article in accordance with a given production schedule.
In conjunction with planning of a production schedule for a given article to be manufactured such as an electric motor, there is known a required material/quantity planning (also known as the material requirements planning, hereinafter referred to also as xe2x80x9cMRPxe2x80x9d in short) as one of methods for automatically determining arithmetically the types or species of parts required for manufacturing an article to be manufactured in accordance with a schedule, time points at which component parts of the article are required and the numbers thereof.
The MRP and the conventional MRP arithmetic scheme is disclosed, for example, in xe2x80x9cZUSETU MRP YOUGO 500 SEN (Selected 500 MRP terms with illustrations in English)xe2x80x9d (published by Nikkan Kogyo Shinbun Co. in 1983) and others. In the following, the conventional MRP arithmetic scheme will be reviewed in brief.
For arithmetically determining an MRP, arrangement/preparation schedule is established on the basis of a planned production schedule of an article level (also known as the master production schedule, hereinafter referred to also as MPS in short) for purchasing or manufacturing required things (items) at required times(within delivery-appointed terms) by required amounts (required quantities) concerning parts, raw materials or the like. This arithmetic procedure requires generally three types of information mentioned below.
(1) MPS
In general, the term xe2x80x9cmaster production schedule or MPSxe2x80x9d means a production schedule and a standard production schedule of an item (article to be manufactured) which occupies a top level in a parts-exploded diagram.
(2) Parts Table
The term xe2x80x9cparts tablexe2x80x9d means a list table based on two types of master data, i.e., data unique to items, being referred to as xe2x80x9citems tablexe2x80x9d, and data indicating interrelations among items, e.g. between an article to be manufactured and component parts, between component parts and component parts, between component parts and raw materials, and so forth, being referred to as xe2x80x9cparts arrangement tablexe2x80x9d.
(3) Inventory/Order Balance
The term xe2x80x9cinventory/order balancexe2x80x9d means inventory and number of items being in process at a current time point or an expected delivery-appointed term and an expected number of items already ordered and expected to be delivered or received in the future (order balance information).
On the basis of the information (1) to (3) mentioned above, the MRP arithmetic procedure is so designed as to execute five arithmetic operations mentioned below f or each of the items.
(1) Total Required Quantity Arithmetic
Required quantity data concerning a relevant item is fetched to thereby determine arithmetically a total required quantity thereof for a time period by taking into account the quantities required on a period-by-period basis. In this conjunction, the following description will be made on the presumption that the period mentioned above is set to one day and thus the schedule is planned on a day-by-day basis.
(2) Net Required Quantity Arithmetic
On the basis of the total required quantity determined arithmetically, the net required quantity demanded on a day-by-day basis is determined arithmetically by taking into account the inventory and the order balance.
(3) Lot Arrangement
On the basis of the net required quantity determined on the day-by-day basis, the number/quantity most appropriate for the arrangement or preparation is determined by taking into consideration a lot size preset for the relevant item.
(4) Lead Time Arithmetic
From the delivery-appointed term of the item of the number/quantity determined through the lot arrangement arithmetic, a lead time is subtracted to determine the relevant order date or outset date to thereby prepare the order.
(5) Expansion of Children-items
The order as prepared is expanded down to the items of the lowest rank by making reference to the parts table. More specifically, the demanded quantity is arithmetically determined for each of child-items on the basis of the child-items and the numbers thereof contained in the data concerning the structure of an article to be manufactured with the date immediately preceding to the order outset date being set as the demand-issued date, whereon the required quantities of the individual child-items are written in the required quantity data of each items.
In the following, the arithmetics (1) to (5) described above will be referred to as xe2x80x9cpart-based expansion arithmeticsxe2x80x9d.
Through the MRP arithmetic procedure, part-based expansion arithmetic is executed for all the items required for manufacturing the articles all preset in the MPS. It is however noted that the arithmetics for the individual items cannot be executed until the part-based expansion arithmetic for the relevant parent-item of the above-mentioned items has been completed for determining the total required quantity as demanded. For controlling such arithmetic execution sequence, low level codes are introduced in the conventional MRP arithmetic procedure.
At this juncture, description will be made of the low level codes in brief, As is illustrated in FIG. 17, on the basis of a parts-exploded diagram of a given article to be manufactured, it is possible to impart level codes to the parts, respectively, in dependence on which of the hierarchical levels or ranks each of the items belongs to in view of the hierarchical parts disposition. Because some of the items may have a plurality of level codes allocated, the level code of the hierarchically lowest level or rank is defined as the low level code. In this conjunction, with the low level or rank, it is contemplated to mean the level as viewed in the direction toward more basic item on the parts-exploded diagram, i.e., when the hierarchical level becomes lower, the corresponding part represents more basic item.
The low level codes of the individual items can be established by retrieving all the items contained in the parts table in precedence to the start of execution of the MRP arithmetic procedure. The low level codes are contained in the items data as the information specific or unique to the items.
By virtue of setting the low level codes in this manner, it can be ensured that so far as the part-based expansion arithmetics for the items ranking hierarchically higher than a given level inclusive thereof has been completed, the arithmetics for all the items belonging to the succeeding level can be executed,
Such being the circumstances, in the conventional MRP arithmetic procedure, the sequence of the part-based expansion arithmetics for the individual items is determined on a level-by-level basis by making use of the low level codes.
More specifically, processings are executed progressively through the procedure described below.
(1) Reading of MPS
A required quantity read out from the MPS is allocated to an item of the article level appearing in the MPS. Further, at that time, the relevant item name or identifier is entered in a queue of level 0.
(2) Start of Arithmetic Operation from the Queue of Level 0.
At the time point when the MPS reading operations have all been completed, one item identifier is extracted from the queue of level 0, whereon the part-based expansion arithmetic is performed for that item, upon completion of which the succeeding item identifier is extracted from the queue. In this conjunction, upon required quantity expansion in the course of the part-based expansion arithmetic operation, the child-item identifiers are entered in the queues of low level codes for the relevant child-items except for the case where the child-item identifiers have already been entered in the queue.
(3) Expansion on a Level-by-level Basis
When the queue of a certain level becomes empty or vacant, one item identifier is taken out from the queue of the immediately succeeding lower level, whereon the part-based expansion arithmetic is performed for the item as taken out. The item identifiers are taken out from the queue of that level until the queue has become vacant, to thereby execute repetitively the part-based expansion arithmetic. As in the case of the process (2) described above, for the required quantity expansion arithmetic included in the part-based expansion arithmetic, the child-item identifier is placed in the low level code queue of that child-item. However, nothing is done when it has already been placed in the queue.
(4) End of MRP Arithmetic Procedure
The arithmetic procedure comes to an end when the queues of all levels become vacant.
In conjunction with the technologies described above, the applicants of the present application has continued the study for speeding up the processing by executing the conventional MRP arithmetic procedures in parallel, the results of which are disclosed, for example, in PCT Publication No. 9629666 entitled xe2x80x9cPARALLEL PROCESSING SCHEME AND APPARATUS FOR MATERIAL/QUANTITY REQUIREMENTS ARITHMETIC USING LOW LEVEL CODES With this technology, the MRP arithmetic procedure is realized through cooperation of a single controller and a plurality of data processing units. Each of the data processing units is designed to execute the part-based expansion arithmetic for each of the allocated items. In that case, when the part-based expansion arithmetic for a given item has been completed with the required quantity of the relevant child-item having been arithmetically determined and when the child-item is to be allocated to the data processing unit differing from that for the parent-item relevant to that child-item, the required quantity of that child-item is transferred to the different data processing unit mentioned just above. While performing such data transfer as mentioned above, the part-based expansion arithmetics are executed for the individual items in parallel as a whole, whereby high-speed execution of the MRP arithmetic procedure can be realized.
By way of example, reference is made to FIG. 18 which shows schematically in a block diagram the configuration of the system disclosed in the above-mentioned publication. When child-items of an item A are represented by items B to G, respectively, and when the items A, B and C are allocated to an MRP arithmetic apparatus 1 while the items D and E are allocated to an MRP arithmetic apparatus 2 with the items F and G being allocated to an MRP arithmetic apparatus 3, there arise problems described below when the parallel processing method of the conventional MRP arithmetic procedure is adopted.
i # Pj: Degradation of Balance in Load of Calculation
It is assumed that the part-based expansion arithmetic for the item A is executed by the MRP arithmetic apparatus 1, as shown in FIG. 18. In the processing for expansion into child-items, the required quantities of the items B to G, respectively, have to be arithmetically determined on the basis of net required quantity data after the lot arrangement for the item A has been done. Consequently, the part-based expansion arithmetic for the item A executed by the MRP arithmetic apparatus 1 involves large load in the processing. On the other hand, processings to be executed by the MRP arithmetic apparatuses 2 and 3, respectively, are absent during execution of the arithmetic by the MRP arithmetic apparatus 1. Such unbalance of the load involved among the MRP arithmetic apparatus upon execution of the arithmetic processings will lead to lowering of the processing speed of the whole system.
i # Qj: Increase of Data Transfer Quantity
After completion of the part-based expansion arithmetic of the item A, a number of required quantity data has to be transferred to each of the MRP arithmetic apparatuses 2 and 3 from the MRP arithmetic apparatus 1, which number corresponding to the number of items allocated to each of the MRP arithmetic apparatuses 2 and 3. The processing time involved in the data transfer means overhead making appearance in the parallel executions of the MRP arithmetics, and thus the processing time of the whole system increases as the quantity of data to be transferred increases.
In the case of the example illustrated in FIG. 18, there exist six child-items for one item. However, in the case, for example, of a printed circuit board having electronic parts mounted thereon, there exist several ten to several hundreds of child-items f or one item. Accordingly, influence of the problems described above becomes serious in a relative sense. Thus, there arises a problem that the processing time can not be shortened to a desired extend even if the MRP arithmetics are executed in parallel.
With the present invention, it is contemplated as an object thereof to provide a material/quantity requirements arithmetic determination system which can ensure enhanced processing speed with the load occurring in execution of the arithmetic processings being uniformized while occurrence of overhead is suppressed to a possible minimum. The object of the present invention can be achieved by providing a material/quantity requirements arithmetic determination system which includes a plurality of arithmetic means for determining arithmetically types of items, quantities thereof and time points at which the items are required, respectively, for manufacturing an article, wherein a first arithmetic means of the plural arithmetic means includes a means for arithmetically determining a net required quantity of the article and a means for outputting the net required quantity determined arithmetically to other one of the plural arithmetic means, and wherein the other one of the plural arithmetic means includes a means for executing child-item-based expansion of an item allocated to that other one arithmetic means by using the net required quantity outputted from the first arithmetic means and means for arithmetically determining a required quantity of the item undergone the child-item-based expansion, whereby at least types of items, quantities thereof and time points at which the items are demanded are arithmetically determined on the basis of the required quantities of the individual items as determined arithmetically for thereby manufacturing the article being subjected to the arithmetic.
Further, the above-mentioned object can be achieved by a material/quantity requirements arithmetic determination system comprising a plurality of MRP arithmetic means for arithmetically determining at least items constituting an article to be manufactured and required quantities of the items, respectively, on the basis of a production schedule of the article, wherein arithmetic determinations of the items constituting the article are allocated to the plurality of MRP arithmetic means which are so arranged as to execute child-items-based expansion for the item(s) allocated thereto.
According to the present invention, it is possible to uniformize load among the MRP arithmetic means because the part-based expansion arithmetics are executed in parallel by the individual MRP arithmetic means for the allocated items, respectively. Furthermore, since the first MRP arithmetic means is required only to transfer the net required quantity of the item to the other MRP arithmetic means, the time required for the transfer can be reduced.
In a preferred mode for carrying out the present invention, the above-mentioned other arithmetic means includes a data holding means for storing data concerning items which the article has, an arithmetic-susceptible item extracting means for extracting child-items which are susceptible to MRP arithmetic, a child-item expanding means for executing child-item-based expansion for the allocated item on the basis of a net required quantity as given, a part-based expansion arithmetic means for receiving data concerning the child-items to thereby execute part-based expansion arithmetic for the child-items, and an arithmetic-susceptible item managing means for supplying to the bart-based expansion arithmetic means the data concerning the child-items extracted through the arithmetic-susceptible item extracting means.
In a further preferred mode for carrying out the present invention, the plurality of arithmetic means are so arranged as to execute in parallel the arithmetics concerning the items for which low level codes representative of level codes of hierarchically lowest rank among those indicating hierarchical levels to which the items constituting the article to be manufactured belong are same.
Further, the object of the present invention can be achieved by providing a material/quantity requirements arithmetic determination method for determining arithmetically types of items, quantities thereof and delivery-appointed terms thereof which are required for manufacturing a predetermined article on the basis of a production schedule of the article with the aid of a plurality of arithmetic means, wherein the method comprises a step of arithmetically determining a net required quantity of the article with first one of the plural arithmetic means, a step of outputting the net required quantity determined arithmetically to other one of the plural arithmetic means, a step of executing child-item-based expansion of an item allocated to the aforementioned other one arithmetic means with said other one arithmetic means by using the net required quantity outputted from the aforementioned first arithmetic means and a step of arithmetically determining a required quantity of the item undergone the child-item-based expansion, whereby at least types of items, quantities thereof and time points at which the items are demanded are arithmetically determined on the basis of the required quantities of the individual items as determined arithmetically, for thereby manufacturing the article being subjected to the arithmetics or alternatively by providing a computer-readable storage medium in which programs for realizing the method described above is stored.